Expert Details

Expert in Thin Film Solar Cell Testing; Semiconductor Optoelectronic Device Measurement and Analysis

Expert ID: 722339 Delaware, USA

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Expert has been involved in research and development of amorphous silicon (a-Si) thin film solar cells for 20 years; in this time he has authored or co-authored over 30 papers. He has guided the optimization of device performance from three different types of CVD reactors: thermal CVD, photo-CVD and plasma-CVD. This lead to his group being the first university group in the U.S. to make a 10% a-Si device (in 1986), which they did using the non-standard photo-CVD. Expert’s group identified the effect of impurities, and buffer layers, as critical. Expert has also collaborated with the three leading U.S. a-Si companies (APS, Solarex/BP Solar, and ECD) in improving their device performance, leading to joint publications with all three. Recently, Expert has specialized in the analysis of light trapping, parasitic optical losses, and TCO/Si interfaces. He has developed unique methods of analysis to identify and quantify where losses are occurring at TCO/p interfaces vs. bulk.

Expert has taught a class for several years on solar electric power systems. This has, by necessity, lead to his study of electric energy systems, focusing on renewable energy systems such as wind power. Issues of intermittent availability and storage are key.

Expert notes that renewable energy (RE) systems must overcome both public perception and investor perception problems. Key issues are the intermittent nature of wind and photovoltaics, and the unavoidable air pollution due to bio-waste or landfill fill gas generation. Expert is involved in advising his state on how to implement RE systems for state facilities.

Expert has been responsible for the operation of a solar cell testing facility for over 10 years. This includes calibration verification with outside labs, designing and assembling new systems, and overseeing the testing of a wide range of solar cell devices and materials. Expert maintains a 1000W AM1.5 global simulator, two IV test systems with low- and high-temperature test capability, a spectral response measurement system, capacitance-voltage, Hall effect, and spectrophotometer. Variation in device contact geometry, illumination requirements, current densities, and stability require a flexible design in all systems. Expert’s group has established very close calibration with national labs. They use four-point IV testing for all electrical measurements to eliminate probe, wiring, and contact resistance issues. Optoelectronic measurements require constant vigilance to ensure that a measurement-related artifact does not influence data. He routinely measures samples from outside industry and provides confidential analysis and interpretation of solar cell material or device performance.

Expert notes that design and manufacture of large area solar panels is the goal of research and development. Issues of throughput, yield, and cost determine the scalability of a given process. Processes having slow deposition rates or long treatments can be paralleled into batch processing although with an increase in equipment costs. Expert has worked with several module manufacturers to evaluate performance of small-area devices cut from production modules. Issues of laser scribing, substrate cleaning, and encapsulation must be evaluated on sub-modules in controlled accelerated stress or other testing since outdoor testing is too variable and slow to yield results. Incorporating processing procedures developed in the lab to give high performance may not be possible in a large area, high-volume production line. For example, graded interfaces and buffer layers may not be directly transferable to the manufacturing floor. Manufacturing is not amenable to controlled experiments. Expert understands these issues and how to reduce them to practice in a high tech, changing process environment.

Expert has been advocating for wider acceptance of solar photovoltaic technology for 25 years during the same time he has been actively involved in research and development. This requires attention to public policy, utility attitude, corporate profitability, and the technology development. He has been involved primarily in the technology development but has participated in various projects or on his own as an advocate for solar technology. Expert notes that based on an experience curve (learning curve) we know that today's silicon module technology is insufficient to meet long-term cost goals. Subsidies and consumer incentive programs will help in the short term but next-generation technology is needed to substantially bring costs down.

Expert assisted in the development of a photoconductive sensor based on thin film a-Si for a biomedical application. He was responsible for designing, fabrication, and testing of specialized devices. Very difficult optimization goals required creative strategies coupled with applying techniques from outside photovoltaics.

Expert may consult nationally and internationally, and is also local to the following cities: Philadelphia, Pennsylvania - Allentown, Pennsylvania - Reading, Pennsylvania - Bethlehem, Pennsylvania - Lancaster, Pennsylvania - Trenton, New Jersey - Camden, New Jersey - Wilmington, Delaware - Baltimore, Maryland - Alexandria, Virginia

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Year Degree Subject Institution
Year: 1990 Degree: Ph.D. Subject: Electrical Engineering Institution: University of Delaware
Year: 1981 Degree: M.S. Subject: Electrical Engineering Institution: Cornell University
Year: 1977 Degree: B.S. Subject: Electrical Engineering Institution: Case Western Reserve University

Work History

Years Employer Title Department Responsibilities
Years: 1982 to Present Employer: Undisclosed Title: Scientist Department: Institute of Energy Conversion Responsibilities: Expert's responsibilities include directing the measurement, testing, and analysis of thin film solar cells. He analyzes results from amorphous Si, CdTe, and CuInGaSe2 solar cell devices. He also develops new measurements or analyses for new device structures. In addition, Expert directs graduate students and technicians.
Years: 1977 to 1982 Employer: IBM Corporation Title: Associate Engineer Department: Endicott, NY Responsibilities: Expert designed and modeled bipolar transistors for custom IC applications. He designed and tested a new Hall effect sensor integrated on a chip. He also provided computer model code to other users in the company for new IC technologies.

Career Accomplishments

Associations / Societies
Expert is a Lifetime Member of the American Physical Society, and a member of the Union of Concerned Scientists.
Professional Appointments
Expert is a Consulting Editor for Progress in Photovoltaics.
Publications and Patents Summary
Expert has over 60 publications relating to measurement, analysis, and design of photovoltaic material and devices.

In addition, he is the editor of a handbook on engineering. He also has two Technical Disclosures published by IBM but not patented.

Fields of Expertise

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